Conductive metal silicides have been used in the fabrication of device components of integrated circuitry. As an example, such may be used to form highly conductive electrical contacts between semiconductor devices and supporting interconnect structures.
One manner of forming metal silicides is to deposit metal into contact with silicon and thereafter heating such materials to cause the metal to react with the silicon and form a low-resistance metal silicide. For example, a thin metal may be deposited over patterned semiconductor devices (e.g., field effect transistors) and over dielectric material such as silicon dioxide and silicon nitride. The materials are then heated which causes a reaction of the silicon of active regions of the semiconductor device, but not with the silicon dioxide or silicon nitride dielectrics. Following the reaction, the un-reacted metal may be removed by chemical etching, leaving conductive metal silicide contacts only over active device regions.
In some instances, it is desirable to form metal silicide with silicon over only some active areas of a substrate and not over others.